The present invention relates to a printed board assembly, comprising a copper coated substrate with electronic components mounted thereon. The substrate with components are sandwiched between resin coated foils thus embedding the components. The invention also relates to a method of manufacturing such a printed board assembly.
EP 0 813 355 (A2) to International Business Machines Inc. relates to a printed circuit board construction with stacked capacitive planes. The entire stack is then covered with epoxy glass to which copper foil is then applied. EP 0 813 355 (A2) does not provide for embedding anything other than flat capacitive planes, having an etched outer surface to which the epoxy adheres and bonds the copper foil.
Similarly, DE-A 196 34 016 (A1) to Taiyo Ink Mfg. Co. Ltd. describes coating a printed circuit board having circuit patterns etched therein with resin and laying a similar etched copper layer thereon which is in turn coated with resin. This reference, as that described above, does not describe anything other than the embedding of flat etched copper sheets.
A printed board assembly is provided comprising a substrate coated with an electrically conducting material, such as etched copper, electrical components being mounted on said substrate, said substrate with components being covered on both sides with resin coated conducting foil, the resin of said resin coated foil facing the substrate and burying said components, said foil being etched with a circuit pattern, a non-conducting material being disposed in the areas between said electrical components.
The present invention enables more components to be packed more compactly within and on the carrier, thereby making it possible to improve the electrical performance, and to integrate the electrical shielding in the carrier. The mechanical stability and strength of the entire assembly is also improved.
According to one embodiment of the printed board assembly according to the present invention, said components are chip resistors and that said carrier is coated between said chip resistors with a sequential built-up (SBU) lacquer. The lacquer is applied in the areas between the chip resistors sequentially until it reaches the level of the top surfaces of the chip resistors, whereupon the resin coated foil is easily applied to the essentially flat surface. This is a very simple and low cost method of integrating chip resistors into the carrier.
According to another embodiment of the printed board assembly according to the present invention said carrier is covered in the areas between said components with a preimpregnated non-conducting resin mat or prepreg covered with a laminate, both provided with holes for said components. This enables the principle of the invention to be applied when higher components than chip resistors are mounted on the substrate. There is either sufficient resin to fill out any remaining space between these higher electronic components, or alternatively, these small remaining spaces can be coated with SBU lacquer before the resin coated foil is applied thereon.
A method is also provided for manufacturing such a printed board assembly, comprising the steps of: mounting electronic components on a substrate patterned copper; covering only the areas of the copper coated substrate between the mounted components with a non-conducting material approximately up to the level of the mounted components, sandwiching the substrate, components and non-conducting material between two sheets of resin coated conducting foil, the resin on said foils facing the substrate and burying said components, and etching circuit patterns in the exposed copper surfaces of the resin coated conducting foils. This is a very economical way of achieving vertical packing of many components in a way which is advantageous structurally and electrically.